CosmicTelescope

Developed by an astrophysicist for astrophysicists, students, and astronomy enthusiasts. Tools for cosmology, gravitational lensing & more. No ads. Offline.

CosmicTelescope is an app developed by an astrophysicist for astrophysicists.

It consists of a toolkit of astrophysics calculators designed to provide immediate access to commonly used tools for astronomy and cosmology to astronomers and researchers (but also students and amateur astronomers).

This app was developed by thinking about the instruments I found myself wishing existed, many times during my own work — "if only an app with this tool existed..."

Everything runs on your device — no account, no internet connection, no ads, no tracking. The app is shared for free, for purely scientific purposes, with the sole hope of giving useful support to friends and colleagues in their work.

This is a first version of an app that is intended to constantly expand its functionalities. Please note that the app may contain errors, so I strongly recommend always cross-checking the results, and please send me any bugs you find at pbergapps@gmail.com.

FEATURES

Cosmology Enter a redshift and a customizable cosmological model, and compute the commonly used cosmological quantities (e.g. age of the universe, Hubble parameter, and comoving/angular-diameter/luminosity distances).

Gravitational Lensing Define a lensing system and compute the physical properties characterizing it (e.g. angular diameter distances, lensing critical surface density, masses). An interactive tool also lets you see the critical curves, caustics, image positions, magnifications, and time delays.

High-z Sources Support for the study of high-z sources: convert between angular size, physical size, and — optionally taking the lensing effect into account — magnification for high-redshift sources, with observed-wavelength and cosmic-time context.

Observations / Survey Planning Characterize telescope pointings and observation FOVs for a custom or preset telescope/instrument, including new instruments and facilities still under construction.

Telescopes Pick a real telescope, then an instrument, then check one or more of its filters or spectrograph coverage, and see them plotted on the observed wavelength axis — photometric filters with their real transmission curves, spectrographs as their real wavelength coverage — together with each band's range, PSF or resolving power, and (at a chosen redshift) rest-frame coverage.

Visibility Planner Helps astronomers prepare their next observation: pick an observatory and target, and see altitude tracks against twilight and Moon conditions, airmass, best observing time, and a "find the best night in the next 365 days" search — with a world map and shareable plot.

Data Archive Browse a comprehensive list of astronomical data archives (including surveys like Euclid) and open them directly in your browser.

Spectral Lines Map known emission/absorption lines into an observed wavelength window for a given redshift, with SED template overlays and the same telescope/filter/spectrograph overlays as the Telescopes tab. Pinch to zoom or drag with one finger to pan the plot.

Unit Converter Convert between the units used throughout astrophysics: wavelength, flux, magnitude systems, angles, and more.

Exposure Time Calculator Helps astronomers prepare their next observing proposal: pick a real telescope, then instrument, then filter (imaging or spectroscopy mode is set automatically), and compute signal-to-noise, limiting magnitude, or required exposure time, with sky-background and cross-band reference-magnitude support.

Physical Constants A reference table of physical constants commonly used in astrophysics and cosmology, with unit toggles.

Every tab includes a short guided tour (with a restart option in the app menu) so new features are easy to discover.

Credits: the development of this app was supported by the power of the most advanced AI tools, including Gemini, Claude Code, and Codex.